In recent years, techniques for forming metal coating using metal nanoparticles as a material of metal wiring have caught much attention. For example, Patent document 1 discloses a method of forming a metal coating having a film thickness of 0.01-1 μm, in which method a metallic paste made by uniformly and fully dispersing metallic ultrafine particles having particle sizes of 0.001-0.1 μm in an organic solvent is applied to a surface of a base material and thereafter the metallic paste is dried and baked.
Also, in Patent document 2, a method of forming a metal coating is described, in which method a metal-nanoparticles-dispersed liquid having a viscosity of 1000 cP or less at room temperature is applied onto a surface of a base material and baked after being dried, wherein the metallic nanoparticle dispersed liquid is prepared by dispersing metal nanoparticles consisting of Ag, or silver oxide, etc. and having a size of nano meter level in an organic solvent, which does not easily evaporate at room temperature but evaporates when heated during a process of drying or baking a coated film, in a manner such that the surface of each metallic nanoparticle is covered with the organic solvent and does not cause agglomeration so that an independent condition thereof may be achieved.
Moreover, in Patent document 3, a method of forming a metal coating is described, in which method a Cu independent ultrafine particles dispersed-liquid having a viscosity of 50 cP or less is applied onto a surface of a base material and baked after being dried, wherein the Cu independent ultrafine particles dispersed liquid is prepared by mixing ultrafine particles containing Cu metal particles having a particle size of 0.01 μm or less and an organic solvent, which does not easily evaporate at room temperature but evaporates during drying or baking a coated film in a process of forming a Cu wiring on a semiconductor substrate, and wherein the surface of each Cu independent ultrafine particle is covered with the organic solvent and the individual Cu independent ultrafine particles are independently dispersed.    Patent document 1: Japanese Patent Application Publication No. H 03-281783.    Patent document 2: Japanese Patent Application Publication No. 2001-35814.    Patent document 3: Japanese Patent Application Publication No. 2000-123634.